Heat transfer system



FIG. 1 is a perspective view of a heat transfer system, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a side elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is an end elevational view thereof;

FIG. 6 is an elevational view of the side opposite that shown in FIG. 3. 

The ornamental design for a heat transfer system, as shown. 